/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} p
 * @param {TreeNode} q
 * @return {boolean}
 */
var isSameTree = function(p, q) {
    if(!p&&!q)return true;
    if(!(p&&q))return false;
    if(p.val !== q.val)return false;

    return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
};